I understand from the Register article that lawyers think the word "sell" could be problematic, since it could be something besides the most obvious understanding. Someone should follow up on what that means, but aside from the following settings, I don't think Mozilla receives any data from your Firefox:

(1) Check your settings on the Settings page under

"Firefox Data Collection and Use"

(2) If you are concerned about how sponsored suggestions could be tailored to your personal use history within Firefox, use the little search box on the page to look for sponsor to find relevant settings.

I don't know what the future holds, but I haven't heard of any browser changes that go beyond those scenarios.

https://blog.mozilla.org/en/products/firefox/update-on-terms-of-use/

TL;DR Mozilla doesn’t sell data about you (in the way that most people think about “selling data”), and we don’t buy data about you. We changed our language because some jurisdictions define “sell” more broadly than most people would usually understand that word. Firefox has built-in privacy and security features, plus options that let you fine-tune your data settings.

Mozilla made a terms of use for Firefox for the first time and now some people are coming to conclusions of Mozilla doing improper things due to how they or others are interpreting things.